As the volume of informational products and applications available on the World-Wide Web (WWW) has increased, the amount of useful information that may be retrieved has also increased. However, for the same reason, the difficulty of locating the information has also increased. As a result, the available information is significantly under-used. Therefore, increasing the efficiency of information retrieval is an important design goal.
Taxonomies are ordered classifications of information, which may be used for organizing information in a way that makes it more accessible for retrieval (e.g., by applications or people). The typical form of a taxonomy is hierarchical. For example, at the top levels of a hierarchy, general terms are used to describe the information. Beneath the top levels, more descriptive terms that refine the top-level terms are used. As such, a hierarchical taxonomy may be represented as a tree of information nodes, in which each node inherits all of its predecessors' attributes, and descriptive terms and other forms of metadata may be used to identify the nodes. Examples of hierarchical taxonomies are the U.S. Library of Congress' subject-heading index, product catalog databases, and WWW directories (e.g., LookSmart®).
An ontology is a vocabulary of terms including precise descriptions of what the terms mean, for the domain they describe and for the computer system, to which they relate. Taxonomies are ordered classifications of terms with support for very few relationships, while ontologies describe in more detail relationships between those terms. Ontologies used for organizing information may be created manually (by persons) or semi-automatically (by computer application).
The process of developing an ontology to organize a relatively large amount of information is exceedingly difficult and time-consuming. Also, once such an ontology has been created, the work of the ontology developers typically does not come to an end. Extensive maintenance of the ontology is required in order to maintain the usefulness of the ontology relative to that of the information in the repository involved. For example, LookSmart® (the second-largest directory on the WWW) reportedly employed about one-third of its personnel in an ontology group in 1999.
Most attempts made to organize information are based on an ideal view of a particular domain or “universe of knowledge”. A classification or ontology developer can create such a view in a logical and well-documented way. Nevertheless, the resulting view is highly subjective and ultimately reflects the opinion of the developer. As mentioned above, a primary goal of organizing information is to make the information available for retrieval. However, because of the numerous different views being used for organizing information, the existing hierarchical classification approaches typically fail usability tests designed for average information users. As a result, a pressing need exists for a technique allowing the developers to adapt their views to those of the users of the system. The users include not only those directly retrieving information, but also the customers utilizing the informational products indirectly, as a foundation for placing online ads, creating online relationships, or supporting online referrals of customers.